Method and apparatus for sidelink data radio bearer establishment in a wireless communication system

Abstract

A method and device are disclosed from the perspective of a User Equipment-to-User Equipment (UE-to-UE) Relay. In one embodiment, the method includes the UE-to-UE Relay receiving a first PC5-Radio Resource Control (RRC) message from a first UE to establish a first Sidelink (SL) Data Radio Bearer (DRB) for a PC5 Quality of Service (QoS) flow, wherein the first SL DRB is used for data transmission from the first UE to the UE-to-UE Relay. The method also includes the UE-to-UE Relay transmitting a first RRC message to a network node to request sidelink resource for the PC5 QoS flow in response to reception of the first PC5-RRC message, wherein the first RRC message includes a destination of a second UE. The method further includes the UE-to-UE Relay receiving a second RRC message from the network node, wherein the second RRC message includes a configuration of a second SL DRB for the PC5 QoS flow, wherein the second SL DRB is used for data transmission from the UE-to-UE Relay to the second UE.

1 . A method for a User Equipment-to-User Equipment (UE-to-UE) Relay, comprising:
 the UE-to-UE Relay receives a first PC5-Radio Resource Control (RRC) message from a first UE to establish a first Sidelink (SL) Data Radio Bearer (DRB) for a PC5 Quality of Service (QoS) flow, wherein the first SL DRB is used for data transmission from the first UE to the UE-to-UE Relay;   the UE-to-UE Relay transmits a first RRC message to a network node to request sidelink resource for the PC5 QoS flow in response to reception of the first PC5-RRC message, wherein the first RRC message includes a destination of a second UE; and   the UE-to-UE Relay receives a second RRC message from the network node, wherein the second RRC message includes a configuration of a second SL DRB for the PC5 QoS flow, wherein the second SL DRB is used for data transmission from the UE-to-UE Relay to the second UE.   
     
     
         2 . The method of  claim 1 , wherein the first UE and the second UE communicate with each other via the UE-to-UE Relay. 
     
     
         3 . The method of  claim 1 , wherein the first PC5-RRC message includes information indicating the PC5 QoS flow is mapped to the first SL DRB. 
     
     
         4 . The method of  claim 1 , wherein the first RRC message includes information indicating an identity and a QoS profile of the PC5 QoS flow. 
     
     
         5 . The method of  claim 1 , wherein the second RRC message includes information indicating the PC5 QoS flow is mapped to the second SL DRB. 
     
     
         6 . The method of  claim 1 , further comprising:
 the UE-to-UE Relay transmits a second PC5-RRC message to the second UE, after the second RRC message is received from the network node, to provide the configuration of the second SL DRB to the second UE.   
     
     
         7 . The method of  claim 1 , further comprising:
 the UE-to-UE Relay transmits a fourth PC5-RRC message to the first UE if a third PC5-RRC message is received from the second UE.   
     
     
         8 . The method of  claim 1 , wherein the first RRC message includes a destination identity of the second UE and/or a cast type of the sidelink communication. 
     
     
         9 . The method of  claim 8 , wherein the cast type is set to “unicast”. 
     
     
         10 . A User Equipment-to-User Equipment (UE-to-UE) Relay, comprising:
 a control circuit;   a processor installed in the control circuit; and   a memory installed in the control circuit and operatively coupled to the processor;   wherein the processor is configured to execute a program code stored in the memory to:
 receive a first PC5-Radio Resource Control (RRC) message from a first UE to establish a first Sidelink (SL) Data Radio Bearer (DRB) for a PC5 Quality of Service (QoS) flow, wherein the first SL DRB is used for data transmission from the first UE to the UE-to-UE Relay; 
 transmit a first RRC message to a network node to request sidelink resource for the PC5 QoS flow in response to reception of the first PC5-RRC message, wherein the first RRC message includes a destination of a second UE; and 
 receive a second RRC message from the network node, wherein the second RRC message includes a configuration of a second SL DRB for the PC5 QoS flow, wherein the second SL DRB is used for data transmission from the UE-to-UE Relay to the second UE. 
   
     
     
         11 . The UE-to-UE Relay of  claim 10 , wherein the first UE and the second UE communicate with each other via the UE-to-UE Relay. 
     
     
         12 . The UE-to-UE Relay of  claim 10 , wherein the first PC5-RRC message includes information indicating the PC5 QoS flow is mapped to the first SL DRB. 
     
     
         13 . The UE-to-UE Relay of  claim 10 , wherein the first RRC message includes information indicating an identity and a QoS profile of the PC5 QoS flow. 
     
     
         14 . The UE-to-UE Relay of  claim 10 , wherein the second RRC message includes information indicating the PC5 QoS flow is mapped to the second SL DRB. 
     
     
         15 . The UE-to-UE Relay of  claim 10 , wherein the processor is further configured to execute the program code stored in the memory to:
 transmit a second PC5-RRC message to the second UE, after the second RRC message is received from the network node, to provide the configuration of the second SL DRB to the second UE.   
     
     
         16 . The UE-to-UE Relay of  claim 10 , wherein the processor is further configured to execute the program code stored in the memory to:
 transmit a fourth PC5-RRC message to the first UE if a third PC5-RRC message is received from the second UE.   
     
     
         17 . The UE-to-UE Relay of  claim 10 , wherein the first RRC message includes a destination identity of the second UE and/or a cast type of the sidelink communication. 
     
     
         18 . The UE-to-UE Relay of  claim 17 , wherein the cast type is set to “unicast”.